Epoxypropyl starch

ABSTRACT

A PROCESS IS DESCRIBED FOR PREPARING NOVEL EXPOXYPROPYL STARCH COMPOUNDS FROM STARCHES AND STARCH DERIVATIVES. AT EPOXYPROPYL D.S. LEVELS OF UP TO 0.09 THE COMPOUNDS ARE WATER-SOLUBLE AND INCREASE BOTH WET AND DRY STRENGTH OF PAPER AT A 1-PERCENT LEVEL OF ADDITION.

. 3,795,671 EPOXYPROPYL STARCH Robert E. Wing, Peoria, and William M. Donne, Morton,

Ill., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Dec. 21, 1971, Ser. No. 210,549 Int. Cl. C08b 19/04 US. Cl. 260-233.3 R Claims ABSTRACT OF THE DISCLOSURE A process is described for preparing novel epoxypropyl starch compounds from starches and starch derivatives. At epoxypropyl D.S. levels of up to 0.09 the compounds are water-soluble and increase both wet and dry strength of paper at a l-percent level of addition.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

BACKGROUND OF THE INVENTION This invention relates to the preparation of starch derivatives and more specifically to starch derivatives containing pendant alkyl epoxides. The invention also relates to the use of epoxypropyl starches as paper additives which increase wet and dry strength.

- (1970). However, no epoxides were formed by attempts to United States Patch 3,795,671 Patented Mar. 5, 1974 anhydroglucose units, in a dimethyl sulfoxide (DMSO) solution; I

(b) reacting the products resulting from step (a) with epichlorohydrin to form epoxypropyl starch; and

(c) recovering the epoxypropyl starch from the reaction mixture.

' Epoxypropyl starch is defined herein to include the products prepared from starch and starch derivatives.

A soluble product is obtained when about 0.18 to about 0.34 mole of NaH is reacted per mole (AGU) of starch or starch derivative. These products will have an epoxypropylD.S. of about 0.03 to about 0.09. At reactant ratios greater than 0.34, the resulting products are water-insoluble. The general formula of the water-soluble epoxypropyl starch products is as follows:

where St=starch or starch derivative having free hydroxyl or starch derivative. These products will have an epoxypropyl group=0.03 to 0.09. The above water-soluble epoxypropyl starches are used in the manufacture of paper. Both the wet and dry'strength of paper is increased when the products are applied at a l-percent level of addition based on dry pulp weight.

DETAILED DESCRIPTION OF THE INVENTION The reaction by which alkyl epoxides are attached to a starch substrate appears to be as follows:

O NaH thrkancrnoi St-OH St-O-Na st-o-cmonorr,

where St=starch, starches, starch products, or starch derivatives that contain free hydroxy groups on the anhydroglucose, units react in accordance with the claimed ,process to produce epoxypropyl starch. 'EXamples of attach alkyl P roups tov the free hydroxyls on the glucose units of starch by reacting allyl starch with peracetic acid [Inano, Chem. Soc. Japan, Inc. Chem-Sect. (Kogyo Kagaku Zasshi), vol. 70, 9, 1550-1553 (1967)] or with a benaonitrile-SO percent hydrogen peroxide solusodium carboxymethyl starch and epichlorohydrin from which he obtained a water-insoluble product containing 1.4 mole percent'carboxymethyl epoxypropyl groups.

The direct reaction of starch with epichlorohydrin in an aqueous alkaline solution is a commercial process which forms inhibited (i.e., crosslinked) starch products resistant to swelling or gelatinization. These products show marked inhibition to hot water swelling with as few as one epoxypropyl group per 1200 anhydroglucose units (AGU) of starch which corresponds to an epoxypropyl as. or 91990315? 2-.. S 240-241 T (1967) for an explanation of the mechanism "of crass:

links in this reaction].

We have discovered a process for pr0duc1ngQepoxy5 propyl. starches w i h can 12s., itherwwa nsolublgggr -ins0luble depending on reaction conditions. It comprises the following steps:

7 (a) reacting sodium hydride (NaH) with a starch or starch derivative, having free hydroxyl groups on the Inhibited starches being essentially insolubl i w fitl.

starches are cereal starches (e.g., corn, wheat, rye, sorghum) and root and root-type starches (e.g., tapioca, potato, waxy maize, waxy sorghum). Examples of starch products are cereal grain flour, grits, and flakes. Examples of starch derivatives as described above are cationic starch [e.g., N-(Z-hydroxypropyl)-diethylamino starch, tertiary 4.5"

tion. Inano was able to achieve a reaction between or quaternary ammonium starch, quaternary phosphonium starch, tertiary sulphonium starch, and aminoethyl starch]; starch ethers (e.g., methyl starch, hydroxyethyl starch, allyl starch, carboxymethyl starch, and 2-cyan0- ethyl starch); starch esters (e.g., starch acetate, starch sulfonates, starch sulfate, and starch phosphate); oxidized starch; and starch graft copolymers. It is understood that examples of starch, starch products, and starch derivatives other than those specifically stated above which react in accordance to the claimed process will be known to those skilled in the art, and that the invention should not be limited to those examples described above.

Thesolvcntinwhich the reaction takes place should be nonaqueous and one in which starch is at least partially soluble} Water should be excluded as much as possible :in order to minimize its reaction with NaH. Starch is soluble in DMSO making it the preferred solvent. Howf amide and tetrahydrofuran.

' rial dissolved in DMSO will theoretically react stoichiometrically with NaH depending on the number of free In the first step of the process the starch starting matehydroxyL groups available. The preferred ratio of NaH to starting material is from 0.2 to 0.7 mole of NaH per 0 AGU of starch or starch derivative which, after subsequent' reaction with epichlorohydrin, gave final products having cpoxypropyl D.S. levels of from 0.03 to 0.14. In

theratio of reactants should b'e'in the raugeofo.1816" 0.34 mole NaH per AGU and the final epoxypropyl starch product should have a D.S. of from 0.03 to 0.09. This-first step' reaction should beconduct ed within a temperature range of from 6 C. to 100 C. These are the melting and decomposition tempratureso'f DMSO. At the preferred temperatures of from 25 C. to 60 C. the reaction will be'c'ornpletewithin about one-half hour. However, reactions were usually allowed to proceed for up to.3 hours. The product of thereactionsbetween-NaH and starch or starch derivatives will herein be calledfsodium-starch. r

. Although epichlorohydrin will essentially react stoichio metrically with sodium-starch, it is preferred that excess epichlorohydrin be used to insure complete reaction. This second step reaction should beco n ducted. at temperatures below 100 C. to minimize evaporation. of epichlorohydrin and because DMSO isstiIIprcsent. The reaction was allowed to proceed for as little as 1 hour and as long as 18 hours at a preferred temperature range of between 25 C to 90 C. Neither temperature nor reaction time appears to be critical. The third and final step in the process for producing epoxypropyl starch is product recovery, which can be performed in several ways such as solvent extraction; The easiest, most convenient, and preferred methodis' based on the products-insolubility in alcohol. After alcohol pre-i cipitation, the'epoxypropyl starch is filtered,'washe'd, and in wet-tensile'l When percent clay was added td'the dried. A cationic starch was reacted with sodium hydride in ratios of from about 0.12 to 0.37 mole of sodium hydride per AGU of cationic starch. Reacting the sodium-cationic starch with epichlorohydrin resulted in a product having an epoxypropyl D.S. of from about 0.05 to 0.08 (see Examples 7-10, infra).

Water-soluble epoxypropyl starches prepared according to the invention having D.S. levels of from 0.03 to 0.09

bonate, sodium bicarbonate, or acetic acid to efiect ring To illustrate the use of starch derivatives asQJstrength- T increasingpaper. additives, a'comimercial cationic starch son, handsheets were "made containing a commercial were tested for their ability to increase paperstr'ength using TAPPI Standard Method T 205 rn-58, Forming Handsheets for Physical Tests of Pulps, T 404. t's-f66, Tensile Breaking Strength of Paper and Paperboard, andT 456 os-68, Wet Tensile Breaking Strengthof Paper and Paperboard. Because of their complete water solubil r ity and their lack of cationic functional groups, epoxypropyl starches prepared from untreated gelatinized' pe'ai'l corn starch were not sufiiciently retained bythecellulose fibers to produce any significant increasesin paper, strength when added to pulp furnishes prior to preparing han'dcationic starch added under identical conditions. Handsheets prepared with the epoxypropyl starch incrcased in dry-tensile strength 27 percent and -wet-ten sile strength- 200 percent'over handsheets made with .a commercial cationic starch. With furnish adjusted to pH 5.5, dry

tensile strength didnot improve, .butwet-tensile strength increased 3.50 percent. Results were similar vwith D.S. 0.048 and 0.076 epoxypropyl cationic starches. Addition levels of 0.25 and 0.50 percent gave smaller increases furnish at pH 5.5, the addition of the cationic epoxy-' propyl derivativeresulted in a l20-percent increase'in wet-tensile and a 34-percent increase'in ash content as compared with a commercial cationic starch. Various treatments of the handsheets after the second TAPPI press to promote further opening of the oxirane ring failed to show any additional strength increase. Evalua tion of these products as spray-on additives by'proc'e dures reported for epoxypropyl starch revealed maximum increases'of- 3 5 and 220 percent in dry-"and wet-tensile strength,"respectively, when comparedy'to the commercial cationicstarch The following examples'are intended to. further illus Y trjat but not limit the invention a claimed.

' Examples 1 6 z 4 hours at 90C. The mixture was cooled and poured into ethanol,(2 liters). The solid was removed by filtration; washed with ethanol (1 liter) acetone (0.5 liter), and hexane (0.5 liter); and dried ina vacuum oven at C.; yield' 9.05.-g., 0.03. D.S. -In other. examples-one or. more variables in ,the reaction were introduced treated with solutions of polycthylenimine, sodiumyear- 60 'Iab le. 1.

Examples 1' '2 3 i 4 '5 "'6 Moisture of pearl starch, percent- 3 is 13 e 2 V 1a 2 13, Weight of ether-washed NaH, g 0.435- 0.23- 0.435- 0.435. 0.435 0.87. genfipezguare of reaction mixture when NaH added, .C gtl 1 m in g y in a f: M t "Dit so fi :Dfi so. :oMso. DMso. nmso. Temperature of mixture when epiehlorohydrln added ,9 C. "I 25 25 525 I Temperature and time of reaction, C.-h0urs p v 90-2 90-2 v 25-18, 90-1- 601 25 18, 90-1. Weight of product, g- 9.05. 8.89. 1 10.56. 9.81; .24- I 11.13. Chlorine, percent.-- 0.49. 0.31.0... 0.54 0.61 0.78.......... 3.96. D.S. cm. 0.09. 0.195- 7 h 0.14. Solubility in water a Soluble- Soluble.'-. Mostly Most ,lnsoluble. insoluble.

- In each example 10.0 g. pearl corn starch was used.

NaH=s0diurn hydride. I

' DMS0=dimethyl sulfoxide.

* Determined by pyridine hydrochloride method of Inano supra. 0 Derivative (1.5 g.) in ml. water at 90 0. for 1 hour; then cool:

" e In eachexample 10.0 g. cationic starch was used.

Examples 7-10 (7) A commercial cationic starch [N-(Z-hydroxypropyl)diethylamino starch, D.S.' less-thzu' 0.05, g.,

9.2 percent moisture] was stirred in DMSO (200'ml.)

for 2 hours at 80 C., cooled to'25 'C., "and sodium hydride (0.165 g.) added as slurry in DMSO (50' ml.).

r mats were mountedin TAPPI standard'rings and placed After an additional 4 hours of stirring, epichlorohydrin inan oven at 75 C. for 1 hour. After drying they were then conditioned and tested for wet and dry breaking length by TAPPI Standard Methods, supra (Table v 3). The basis weight of handsheets was 60 g./rn. I

TABLE 3 V m.) of handsheets treated with epoxypropyl starch] [Physical testing (breaking length,

" Epoxypropyl starch (D.S.)

' 0. 09 Control j Treatment l Dry Wet Dry Wet Dry Wet Dry I Wet Dry W t Dry w t None 6 7, 940 155 ,283 250 8, 294 500 r 8,152 495 7,734 550. 6,- 879 100 ater 7, 100 125 6, 904 235 7, 772 555 8, 019 425 7, 437 395 892 130 4% N23200:- 0, 440 150 295 305 7, 170 870 7, 448 555 7, 300 640 5, 567 150 4 a NaHCO; 6, 590 140 6, 278 270 7,138 690 7,107 560 7,238 725 4,796 135 2% NaHCOs plus 2% NazCO 6, 200 150 5, 970 300 7, 713 835 7, 886 645 7, 841 795 5, 643 125 4% Et N 7, 170 130 6,866 185 7,310 515 6,892 420 7, 451 510 5,738 110 1. v 6,850 l 200 6,566 555 7, 557 900 7, 713 815 7,102 805 5,882 180 4% CH3COOH 6, 450 165 6, 381 240 7, 995 730 7,820 505 6, 984 700 5,457 120 I Added to about 1 g. wet pickup.

b About a I-percent addition.

' Untreated gelatinized pearl corn starch.

d No chemical spray applied.

- Polyethylenimine-moiecular weight, 600 (Dow Chemical 00.).

( ml.) was added and the mixture was stirred for Example 1 18 hours at C., then 1 hour at 80 C. The mixture was cooled and poured into ethanol (2 liters). The solid was removed by filtration, washed with ethanol (1 liter),

acetone (0.5 liter), and hexane (0.5 liter), and dried.

in a vacuum oven at 60 0.; yield 9.4 g. Anpxiran'eanalysis conducted by the pyridine hydrochloride method of Inano, supra, gave an epoxypropyl content which corresponded to a D8. of 0.048. In other examples the ratio of reactants was varied to give products of difierent D.S. (Table 2).

TABLE2".',@;..,....

Examples 7 "s' 9* g 10 Weight ofether-washed NaH 0.105 0.33 I 0.50" 0'30 Weight ot mduc n 3. g 3.3g s ag: 3.30

o J a e chloflne'percen 004810.005 0.076 v 0.004

Epoxypropyl D.S.

Temperature and time of reaction C.-hour); 25-18 then 80-1. g

b NaH=sodium hydride. Cationic starch =0.78 percent chlorine. 1 4 Determinedby pyridine hydrochloride method 01 Inano, supra.

f if" Unbleached graft pulp was re fined in a 5- 1b. Valley heater to a freeness of 590 ml. CSF. Wet paper mats were prepared at-pH'7 in a British'sheet'machine, pressed 1 to TAPPI Standard Methods, and used without further drying. At this point solutions 01 the epoxypropyl starch products from Examples i-4 were prepared by placing 1.5 g. of each product in 100 ml. of;water;and-sti i ng at C. for 1 hour. Each solution was cooled and applied to the wet paper mats by spraying with a bottle sprayer under constant air pressure to a level of about 1 percent starch based on the dry weight of the cellulose V1 percent consistency and diluted to 6150 g. with tap water." With continuous mixing, the additives (0.15 g./ ml.water) were added to the pulp slurry and the pH was'adjusted with 10 percent sulfuric acid. Hand- TABLE 4 [Breaking length, m. of handshe ets treated with epoxypropyl cationic Standard TAPPI conditioning Dry Wet 6,260 160 7,400 165 I, 7, 410 735 7, 735 1% 0.076 D.S. 7,380 805 0.25% Cationic starch 6,570 0.50% Cationic starch 7, 020 0.25% 0.048 D.S.- 6, 740 350v 0.50% 0.048 D.S.'. 6, 890 440 I Applied as wet-end additive. Y

Samples were stirred in water (100 ml.) at 90 C. for 30 min. before adding to furnish at various levels.

a D.S'. ref erslto epoxypropyl DB. of certain epichlorohydrin-treated cationic starch samples. J 6 Thirty-minute immersion in distilled water (or wet tensile.

" Ne(2hydroxypropyD-diethylamino starch.

1 Product of Example No. 7.

Product of Example No. 8.

11 Product of Example No. 9.

1 Product of Example No. 10.

p p (b) reactingthe products resulting from step a),.. with 'TA'BI EIFT f V E LLB reaidnglength, In. and ash content of handsheets treatedizvith 'epoxypropyl cationic starch and clay I A ,f Treatment U Standard "2%Nszco5 Y; TAPPI 4hr. .1om1n., 2%NaHC O1,- I

methods I we; 4 11 1,75 o. 7 Ah Sample evaluated Dry Wet Dry Wet Dry Wei; Dry Wet perc nt v 160 6,130 170 6,070 160 5,780 200 1. 15 6,320 6,230 150 5,500 180 0.86 170 6,610 185 6, 310 195 5,440 220 1.39 7,030 205 6, 730 180 6, 420 220 1.29 7,980 205 7,870;;; 200 7,680 260 1.69 b d-$0.064 D.S.d .s .380 7,390 490. .7,.720 470. .7,100 585 2.27,.-

.JAppliedas.wet-end-additiveimpercentclay.-

Varloustreatments after second TAPPI press. j g- @Sprayed onto-a1 g.wet-pickup aftersecond TAPPI press. H r-iggmples o1 N-(2hydroxypropy1)-diethylamino starch (0.15 g., d.b.) were, stirred in water (100 ml.) at 90 C. 1 I

or .m n, A m, 1x h r 1 r '.D.S. ot'epoxypropyl cationic starch of Example 10.

v v EXAMPLE IS f .(c recovering said epoxypropyl starch from the reac p tionmixt'ureJ The product of ExampleJO was appl ed to .wet paper v 1 4. A process for preparing epoxypropyl starch as dematsmasdescrihed.1n.Examp1e.-1 1.and testedionbreakmg. '1.finedin..c1aim13 in whilii odiun'i..hydr'ide is present in length, Table 6. 25 amounts of frorr10.18to 034 111011: per anhydroglucose TABLE 6 [Breaking length, m. of handsheets treated with D.S. 0.064 epoxypropyl cationic starch as a spray-on additive] c n m 0.064 D.S. l

8 0 O epoxy l'O Control starch cationic stag he Treatment pH 7.0 Dry Wet Dry Wet Dry None 0 6,880 205 0,270 195 7,280 Water 6, 200 205. 5, 720 185 7, 000 4% N11200:"..- 5,850 230 5,315 210 6, 840 4% NaHC 0; 6, 390 230 5, 225 7,430 2% NagCO; plus 2% NaHCO:.. 6, 200 245 5 640 210 7,360 5, e70 51810 2 7,430 47 PEI 6 6, 460 300' 5, 480 280' 7,360 1 CH=CO0H 6,150 215 5,270 1.185 0,920

I Added to about 1 g. wet pickup; then dried 1 hour at 75.90.

b About 1 percent addition.

I Nochemical spray applied. d Bol-yethylenirnine-molecular weight, 600 (Dowflhemical, Co

'.,We claim: i I I 4- units of the starch and epichlorohydrin is present in 1. As, a composition of matter, avatar-soluble .epoxyr amounts suflicientto produce epoxypropyl starches having propyl starch comprising the followmg structure: epoxypropyl D.S.s of f10m ,0.03Tt0 0.09.

7 Q "'sfi rpfo cessfrpr preparing Y epoxypropyl starch-"as dened-in claim d-mwhich.thestarchisa.cationicstarch,

where St-"isstarch or starch derivativeshavingfree hy- 5 mqle gghydrgglucose ultit of cationicxstarbh droxyl groups onthe anhydroglucose units, and D.S. is :andjplchlomhyglmllslgqwm'"Lagmuntsiisufliplfmtt? 003 {0.009; 55 producecpoxypropyl. tarcheshavmg epOXYPropylDS. s

f 0.05 to 0.08. 2. ThewaterV-soluble epoxypropylrstarch.,of'claim 1 1n 0 Which St is cationic starch, and D.S. is 0.05 to 0:08.

f? 1 F 3. A process for preparing epoxyprop'yl starch corn- UNITED STATES PATENTS prisingthe following Step 1 I 3 414,530 12/1968 Zlkh t a]. 26 23 .3 R

(a) reacting sodium hydride with starch or. starch de- 60 1 a e 0 3 riyatives having free hydroxyl groupsjon the anhy- OTHER droglucose units in a dimethyl sulfoxi olution at Wi t 1, c b p d R h, l, 12, 235-.

temperatures'of 6 to 100 C. 150005910 3 hours, "'2"89 "(1970). said sodium hydride being presentiniamounts of from if 5 about 0.2 to 0.7 mole per anhydroglucqse pnit of the 65 BONALD'E; CZAIA, Primary Examiner starch; a;

ssist ant'Examiher' 1 epichlorohydrin at temperatures of 25?;0907 for 1 to 18 hours, said epichlorohydrin beingpresen n;, i amounts suflicient to produce epoxyp ifopyl' arh'e's having epoxypropyl D.S.s of from 0.0 

